Chondrocyte proliferation and expression of differentiated function are important in the process of prevention and treatment of various cartilage diseases. In other words, it is believed that the proliferation and maturation of chondrocytes lead to the normal growth of bones and the restoration in the case of fracture. TGF-β1 (Transforming Growth Factor), IGF-1 (Insulin-like Growth Factor), bFGF (basic Fibroblast Growth Factor), PTHrP (PTH-related peptide: parathyroid hormone-related protein), HGF (Hepatocyte Growth Factor), BMP (bone morphogenetic protein), etc. have been reported as factors to induce the proliferation of chondrocytes. However, clinical application of chondrocyte proliferation promoting agent with excellent safety, stability and efficacy has not been established.
The disease with a highest number of patients is osteoarthritis in the cartilage diseases. Aging is considered to be one of the causes, and the increase of the said disease is expected in the aging society in the future. Although bone resorption inhibitory substances such as estrogen and calcitonin, aspirin and non-steroidal anti-inflammatory agents (NSAID) have been conventionally used for the prevention and treatment of cartilage disorders in which cartilage degeneration such as joint diseases is the main lesion, they have never shown sufficient effects and in addition even adverse effects such as gastrointestinal disorders are well known. Therefore, preventing or ameliorating agent safely used in the treatment of cartilage damages and cartilage disorders has been strongly required.
On the other hand, inventors of the present invention have studied the function of the egg yolk protein hydrolyzate, and have found an antioxidant effect (Patent Literature 1), and a bone strengthening effect (Patent Literature 2) and the like. However, effects on cartilage have not been reported.